MartinLogan Impression ESL 11A Electrostatic Speakers Review

The speakers reward the fulfillment of those requirements with amazing performance. If you have the income and desire to hear one of the best, then you must audition the MartinLogans.

Electrostatic speakers have also traditionally been known for their inability to produce the bass of conventional cone speakers. Other companies have tried hybrid designs using cone bass and electrostatic midrange/treble, but the crossovers have usually been audible with the bass sounding slower and heavier than the higher frequencies.

Through the use of new technologies and dedicated engineering, the ML speakers have mostly eliminated the audible disconnect between cone bass and electrostatic higher frequencies. How successful have they been? Read on…

LINKS:

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• ML Classic ESL-9 Speakers
• ML Soundbars
• ML Vision-X Soundbar
• ML Renaissance 15A Speakers
• ML Electromotion ESL-X Speakers
• ML Atmos Speaker And more…

As mentioned previously, MartinLogan does two unusual things with their ESL 11A speaker. First, the Curvilinear Line-Source technology allows far broader dispersion in the treble than the usual panel speaker and second, the hybrid, self-amplified cone bass section allows them to carefully control the transition between the bass and the rest of the frequency range.

The CLS technology is a mature, proven and reliable innovation that to the best of my knowledge, is unique to MartinLogan. It works well, and supplies up to 30 degrees of horizontal midrange and treble dispersion. The electrostatic panel is curved, bowing outward at the front and center so that all midrange and treble frequencies are dispersed broadly.

At the 300Hz crossover, multiple low-pass filters are used to prevent audible overlap between the electrostatic and traditional cone parts of the speaker. Because the electrostatic panels (a membrane just 0.0005 of an inch thick) have far less mass than the woofers, overlap would tend to blur the sound. The 300Hz crossover frequency is one that the ear is highly sensitive to, and any blur there would be immediately noticeable. But by using filters in this way, overlap is reduced and so is the blurring.

The two woofer cones provide both direct and reflected sound that is intended to blend better with the electrostatic panels’ dipole radiation pattern. Having the woofers adjacent to the floor allows not only for better coupling but it also avoids the strong first reflection that happens when woofers are elevated above the floor.

Using an internal amplifier to power the woofers further enhances control and allows the main audio amplifier a much easier drive. The bass frequencies that require high current are being serviced by the speakers’ internal amps. In effect, the main amplifier need only reproduce from 300Hz on up. That makes this hybrid speaker FAR easier to drive than a conventional full-range model. During some of my listening, I drove the ESL 11A’s successfully with a pair of 15-watt, mono-block tube amplifiers.

The transparent electrostatic panel is far less conspicuous than you might think, and these speakers easily blend into most home decors. And finally, they are available in a variety of colors:

My review pair was in black with lovely walnut bass bins. ML has made a very smart design choice here and one that I wish other manufacturers would emulate. Around the bottom of each bin is a roughly three-inch high strip of black metal alloy. It protects the woodgrain finish from the assaults of vacuum cleaners. That short skirt prevents the veneer from being marred by repetitive household cleaning. Well done!

MartinLogan claims several advantages for their speaker design:

Curvilinear Line Source (CLS) Transducer – Since the beginning of audio, achieving smooth dispersion has been a challenge for all speaker designers. Large panel transducers present unique difficulties because the larger the panel, the more directional the dispersion pattern becomes. By curving the horizontal plane of the electrostatic transducer, a controlled horizontal dispersion pattern could be achieved.

Generation 2 Diaphragm – The electrostatic diaphragm employs a coating applied to the polymer surface at an atomic level using a plasma bonding process. A proprietary conductive compound is driven into the surface of the polymer film in an oxygen free argon chamber. This process allows extremely uniform surface resistivity characteristics, an optically transparent surface and a nearly massless diaphragm. As a result, no discharging or arcing can occur.

MicroPerf Stator – This reveals more open playable area in each panel, offering increased performance from even more compact stat panels. It is significant to note that the ML transducer supports the bandwidth and dynamics associated with traditional electrostatic panels nearly twice its size.

Vacuum Bonding – Two insulated high-purity carbon steel stators along with a proprietary plasma bonded diaphragm and ClearSpar spacers are fused into the curved geometry with an adhesive whose strength exceeds that of welding. The process guarantees uniform diaphragm tensioning and extremely precise construction tolerances, resulting in linearity and efficiency.

AirFrame Technology – The panels are joined to their speaker cabinets using extruded aluminum. This provides rigidity without obstructing the playable surface or interfering with the dipole sound radiation pattern.

Poweredforce Forward Bass Technology – Low-frequency equalization, integrated into Poweredforce technology, allows calibration for optimal room integration. In traditional speaker systems, the reflected low-frequency energy from the wall behind the speakers recombines with the energy projected forward causing booming and/or lean bass. ML’s two horizontally-opposed, phase-timed drivers are said to reduce the reflected energy.

Anthem Room Correction (ARC) Technology – An optional ARC box features a calibrated microphone that measures the woofer’s output in the room, comparing it to optimal response curves. The advanced DSP adjusts the speaker’s output to accommodate the room’s unique acoustics and the speakers’ locations in the room.

The speakers arrived as freight on a pallet. Even after removing the two boxes from the single pallet, this is NOT a pair of speakers that should be moved, unpacked or set up by one person. For this reason, MartinLogan dealers have set up and delivery services available.

I got the boxes home, then consulted the owner’s manual for unpacking instructions. The cartons are thoughtfully marked with “open other side” text that coaches the owner in the right direction. But the manual’s instructions for how to unpack consist of a graphic and a single sentence, “Unpack and set up the speakers.” Nevertheless, I got it done, then plugged them in so they could charge and stabilize.

The owner’s manual for the 11A’s recommends starting with the rear of the speakers placed approximately two to three feet from the wall behind them and the edges of the electrostatic panels at least two feet from the side walls. The listening distance should be further than the distance between the speakers themselves. Of course nothing is perfect, and I had to start with my speakers about a foot and a half from the rear wall. Fortunately, they seem to work fine there and imaging was great.

Note that the more damping material you have on the wall behind the speakers, the closer you can get away with moving the speakers to the wall. Heavy drapes or a tapestry would be ideal, but I used some commercial two-inch thick audio absorber pads.

The owner’s manual also recommends aftermarket power cords. Why the supplied power cords are considered substandard isn’t mentioned, nor why aftermarket cords should be needed for a ten-thousand-dollar product. I had some heavy-duty 12awg IEC cords in my parts bin, so I used those and left the ML cords in their boxes. I also tried some lighter gauge cords without any apparent reduction in performance.

The tilt of the electrostatic panels can be adjusted to provide the best imaging regardless of seating height. I found that the out-of-box tilt was perfect for my couch.

As to break-in, the manual advises, “Our woofers require approximately 72 hours of break-in at 90dB (moderate listening levels) before any critical listening. The break-in requirements of the crossover components (and, to a lesser degree, the stator) are equivalent.” My three days of irritating noise were done before critical listening began.

Note that ML does not provide bi-wire terminals. So all your fancy bi-wire speaker cables are only “half usable.” The single terminals are fine, though, and I used mine exclusively with banana plugs. Some high-end manufacturers (including the late, great Jim Thiel) have stated that there is no significant audible advantage to bi-wiring, and that they don’t include it on their products. Martin-Logan obviously agrees.

The manual also provides instructions on use of the Anthem Room Correction or ARC. This is an optional package that electronically removes room peaks and corrects for left/right imbalances. Since this was not included with the review sample, I can’t comment on it

The manual also includes a good discussion of room acoustics and acoustical treatment. Spikes are included with the speaker that are fine for carpet, but would readily damage wooden or vinyl floors. Fortunately, the pre-installed feet provided by ML are rubber hemispheres, and I used those.

The lower midrange and bass frequencies (below 300Hz) are handled by the ML’s internal amplifier:

The two 8-inch long-throw woofers (front and rear) reproduce the low frequencies:

Mid-bass can be controlled by a switch (-2dB/Flat/+2dB), and the low bass by a dial (plus or minus up to 10dB). These can be used to fine-tune the speaker to the room.

One of the first things that I noticed about the MLs is that I had forgotten how clean and extended an electrostatic midrange/treble could be. I’ve lately owned and listened to a wide variety of very high quality cone-and-dome speakers, including the Axiom Audio M100 and the Tekton Pendragons. Both of these conventional designs have excellent treble. But the ESL 11A speakers are in a whole different universe.

I have come to think of these speakers as “amplifier debunkers.” Whatever the amplifier sends these speakers comes right on out. A substandard amp has absolutely nowhere to hide. An amp with a slightly-recessed midrange (I had one of these on hand – a Class-D pro power amp) is revealed as having not only the glassy midrange but also the less-than-dynamic, rolled-off treble that one might expect from a pro amplifier.

For part of my listening, I used a historically popular tube power amp, the Dynaco ST70. My amp came to me modified, and has a very slight midrange/treble glare. This glare is but a slight irritant when used with less revealing speakers, but the amp’s shortcoming became painfully obvious when played above background levels through the MartinLogans. This had nothing to do with the electrostatic technology either – I’ve noticed the glare of this particular amp through both of my cone-and-dome Axiom and Tekton speakers. But the transparency of the MLs made it even more obvious.

One great-sounding pair of mono-block amplifiers that I found for the MLs are a pair of Heathkit EA-2 amps that I modified (from monophonic integrated amplifiers to monophonic power amplifiers) myself. They put out about 12 watts per channel. The superiority of these amps was painfully obvious, and on almost any music. And although below the recommended wattage for the MLs, the Heathkits played more than loudly enough for my ears. These were tied for my favorite amplifiers for these speakers.

My other favorite amplifier, and one that made the MLs really sing, was the new Cary Audio SI-300.2d (Secrets review coming soon). This solid-state integrated amplifier with onboard DAC showed its quality even on these very-revealing speakers.

I wanted to try another pair of amplifiers with the ESL 11As – a pair of solid-state mono block units with a significant amount of Class-A power. But unknown to me, their bridged design made it unsuitable for impedances below two ohms. The 11A speakers fall to 0.6 ohms at 20KHz.

And this brings up a warning – ensure that your amplifier can handle low-impedance, reactive loads before hooking up the ESL 11As. If you have any doubts, check with the amplifier manufacturer and/or MartinLogan. Incompatible amplifiers are relatively rare, but the cost of amplifier repair or replacement can be considerable.

The MLs never sounded bad, even with the most modest of amplification, but they definitely revealed the sound quality of the source and amplifier feeding them. A good upstream source/preamp/power-amplifier will be well worth the money. This isn’t always the case – some speakers are low-resolution enough that they can sound their best with any group of electronics. Lesser amplifiers won’t sound any worse with the MLs, but due to the high transparency of the speakers, good sources and amps certainly justify their cost.

Associated equipment used for this review:

• MacBook Pro running JRiver Media Center 22
• Red Book CD collection ripped in WAV format
• Oppo BDP-105 used as a DLNA (Ethernet) DAC
• SACD discs played via the Oppo
• Schiit Gungnir Multibit DAC
• PS Audio PCA-2 solid-state preamplifier
• Dynaco ST70 tubed power amplifier (modified from stock configuration by previous owner)
• Heathkit EA-2 tubed amplifiers (converted to mono-block power amps only)
• Unnamed pair of solid-state mono-block amplifiers (too unstable for speakers)
• Crown XLS-1000 Class-D pro power amplifier
• Cary Audio SI-300.2d integrated amp with built-in DAC
• Interconnects from Audioquest, Emotiva, BlueJeans Cable, and others
• 12awg IEC power cords from Parts-Express
• Speaker cables from BlueJeans, Nordost Flatline, Straightwire Symphony SC, and others

So how do the MartinLogan ESL 11A’s SOUND? It’s harder to describe than you might think. The speakers, with their bipolar radiation pattern, demand a symmetrical room. Any unavoidable right-to-left imbalance must be compensated for (but imperfectly) via a balance control. It is possible however, that the Anthem Room Correction (ARC) could provide more effective correction. My advice is that if you’re going to spend the money on these speakers, make sure that you have a symmetrical room to put them in. Fortunately, my room is symmetrical from left to right, and the speakers imaged wonderfully there.

As mentioned before, the owner’s manual also recommends that the backs of the speakers be a minimum of two to three feet from the wall behind them. This means that the speakers will NOT be inconspicuous. They’re not small to start with, and being so far forward into the room space makes them even more prominent. The placement requirements make these speakers an impediment to using them in many multi-purpose rooms. Don’t buy these to shove against the wall in your living room. The speakers need a dedicated listening room and preferably a BIG one. Now that said, I found that with judicious adjustment (and by using the included bass controls) I could get away with the speakers being as little as one foot from the wall behind them. This is not a recommended placement, but it can work. Having ATS Acoustics absorbers on the wall behind the speakers definitely helped by making near-wall placement more feasible. Without the absorbers, the strong rear-wave reflection would have blurred the sound. My auditioning was done with the speakers anywhere from one to (more of the time) two feet, and occasionally three feet from the wall behind.

The ESL 11A’s can sound anywhere from lean to boomy, depending on the adjustments of the mid-bass & low-bass trims on the speaker. Remember that its internal amplifier is reproducing everything below 300Hz. But the drive signal is coming from the source amplifier at speaker-level, not line-level from a preamp-out. Therefore, the character of the source amplifier is maintained from midrange to bass, and there is no discontinuity where the 300Hz crossover occurs. Starting with all switches & dials at their zero positions, I ended up needing no bass boost in my room. Keep in mind that for larger rooms, MartinLogan does offer two speaker models with larger woofers – the Expression ESL 13A and the Renaissance ESL 15A. And for smaller rooms, the Classic ESL 9 is also available. The 11A worked fine in my room and delivered very smooth bass response.

The MLs are as clean and transparent as you’d expect from an electrostatic speaker. No cone and dome speaker I’ve ever heard can compare. The only negative, if you want to think of it as that, is the bipolar radiation pattern of the ML creates a more generous but slightly less precise image than does a point-source radiator (such as for example, the Thiel 3.7). If an analytically precise image is your Holy Grail, then perhaps the MLs aren’t for you.

The MLs sound ethereal and completely divorced from their physical positions. For example, when a cymbal or bell is struck, the sound seems to float over the orchestra exactly as it does at the symphony hall. This is HIGHLY unusual and the MLs do it perfectly. Other percussion instruments are similarly well-reproduced – think drumsticks, rim-shots, xylophones, and cow bells.

It’s fair to say that I spent a LOT of time listening to the ESL 11As. Many recordings revealed different aspects of the speakers’ performance. I listened to the following selections (among others):

I’ve spoken before about the veracity of cymbals, bells and percussive sounds through the ESL 11As, but the four cuts that I thought exhibited their treble performance best included:

Summertime by Janis Joplin (with Big Brother & the Holding Company). The brushed cymbals and light taps sound like a real drum kit right in your living room. Many speakers have difficulty with treble. To my ears for example, Klipsch Heritage speakers get the brass right, but lack some of the overtones that should be there. B&W speakers on the other hand, miss the brass and sound too “tizzy.” The ESL 11As get both the brass and the ringing overtones just right.

Cyril Neville’s album, New Orleans Cooking, contains the cut Tipitina. Again, in my room, the cymbals hit exactly the right balance.

The Journeyman album by Eric Clapton has the chestnut Pretending. Percussive sounds seemed to jump from the mix and were extremely airy without being too tizzy.

And Frank Sinatra’s Fly Me To The Moon never sounded better with its drumstick introduction and the amazingly well-recorded band with percussion sounds that swell and dip.

The midrange is where the voice lies. Get the voice wrong (many speakers do) and no matter how great the rest sounds, the speaker’s a failure. The lovely ESL 11As get voices right all the way from the bass to the soprano.

One of my guilty pleasures is Balkan Beat Box. Their Blue Eyed Black Boy album has the cut Dancing With The Moon. I like the video, and have found that I enjoy listening to the audio as well. The singer is a tenor, and despite the fact that no vibrato is employed, the tone is as natural as I’ve heard.

David Clayton Thomas’ baritone is displayed on the Blood, Sweat and Tears album by the cut Sometimes In Winter. Both the roughness and the texture of the voice are on display, and the voice never sounds as if the singer is moving back and forth from the microphone with differing frequencies as it does on speakers with uneven midrange response. The comment I can make is that with the ESL 11As, the singer sounds as if he’s in the room with you. Nice.

From the Chris Isaak album Heart Shaped World comes the undeservingly less-than-famous Blue Spanish Sky. Chris can sing all the way from baritone to falsetto – and never sound funny doing it. His voice never sounds artificial on this track, despite the wide vocal frequency range. The ESL 11As make it sound as if a real person is singing in the room, and when the trumpet comes in at the end of the song, it is sufficiently ethereal-sounding to make your hair stand up.

The live performance of Seven Bridges Road by the Eagles shows the resolving power of the ESL 11As. Some speakers blur the voices so that you hear the harmony, but not necessarily the individuals that are singing. With these speakers, there is sufficient resolution to pick out each individual line and still appreciate the harmonic interplay.

I sometimes like pipe organ and synth music – and the 11As can do that; energizing the room even without subwoofers! But a great speaker must also maintain both pitch and resolution in the bass frequencies. Many can’t.

For a bass slam not to be missed, play Malaga by Armik. When the initial notes are struck the 11As energize the entire room with bass while still maintaining pitch. Something that FEW speakers can do.

With the Atlantic Brass Quintet’s Hungarian Rhapsody No. 2, the tuba notes are fat and have great body – sounding just as a real tuba would.

The classic Baroque and Blue from Claude Bolling’s Suite for Flute and Jazz Piano disc provides acoustic bass in a well-recorded venue. With the 11As, I hear the initial pluck of the string, the tone of the note (with clarity) and the decay. What these speakers do that many others can’t, is separate the bass from the other instruments and provide it with its own tone, pitch and definition.

I also enjoy the Haydn Symphonies The Clock and London by the Orchestra of St. Lukes, directed by Sir Charles Mackerras. There are timpani, brass and string bass, all of which are particularly tactile through the 11A speakers.

The very finely recorded Western Standard Time CD by Asleep At The Wheel contains the classic Hot Rod Lincoln. This was a studio album, and its clarity shows. Ray Benson’s voice and guitar work should be front and center, and with the ESL 11As, that’s exactly where it is. The music swirls, but the imaging is clear.

Clay Jones’ Mountain Tradition CD contains the cut Under the Double Eagle that should put the guitar in your room, and at the center. The ESL 11As do just that, and with amazing verisimilitude – if you can’t close your eyes and hear the guitarist in your living room, then something’s wrong.

The vintage Season of the Witch by Donovan should sound so present that it’s spooky. This is another cut that should raise the hair on your neck. The ESL 11As deliver on the “virtual reality” of this song.

The country classic, Golden Ring by George Jones & Tammy Wynette is yet another example of a studio recording that conveys great presence. Try it and see!

The imaging of the 11A speakers also does holographic things with recordings in Q-Sound (Madonna’s Immaculate Collection, and Roger Waters’ Amused to Death to name but two). The broad, immersive image works well and some sounds actually seem to come from behind the listener.

Note that I haven’t listed any of the four above attributes (treble, midrange, bass or imaging) as the best. This is deliberate. The ESL 11As are so well balanced that I can find no specific acoustic weaknesses. Few speakers that I’ve ever heard are so balanced. And in a word, I’d say that “balance” defines them just fine. You want to know what you get for ten-thousand dollars that lesser speakers don’t have? That’s it – balance. These speakers are somewhere between very good and great at every level. Less-expensive speakers can rival or even surpass the MartinLogans in one category, maybe even two – but nothing I’ve heard for less can match them in every aspect.

The ML’s bass audibly extends to about 25Hz in my room. Is this an artifact of the source amplifier or the speaker? To find out, I ran a low frequency sweep using the Cary Audio SI-300.2d integrated amplifier. Results were measured via Galaxy Audio Check Mate SPL meter – IEC 651, Type II – A-weighted. The microphone was placed one meter from the front of the speaker and 29-inches off the floor (approximate center of speaker from top-to-bottom). For measurements, the speakers were placed two feet from the back wall. Bass results are averaged between right & left, and between three sweeps of each speaker to eliminate outlying data:

Since bass measurements (particularly in-room) are difficult, don’t attach too much significance to the above data. I think that most of the variation is due to room effects.

I also used a full-spectrum pink-noise sweep using locations as in the bass sweep except that Real-Time Analyzer software was used. For this, flat weighting was used rather than A-weighting. Using the Cary Audio integrated amplifier, 1/3-octave results are as follows – again, results are averaged between the right & left speakers:

MartinLogan doesn’t publish impedance, phase-angle or frequency response curves for this speaker. However, they do state that their impedance dips significantly at higher frequencies. This low impedance, (0.6 ohms at 20KHz) with a corresponding increase in phase-angle suggests that amplifiers that aren’t stable into low impedances shouldn’t be used. But in practice, I found that the speakers seemed perfectly happy with a wide variety of amps (with only one exception). Now if you want auditorium levels from the speakers, then more attention should be paid to amplifier power capacity and low-impedance stability.

MartinLogan’s online FAQs recommend an amplifier that doubles in wattage between eight and four ohms and again increases its wattage at two ohms. This would seem to eliminate most amplifiers from consideration – but unless you push the volume limits, this advice can have some flexibility. Most high-quality amplifiers of tube or solid-state design should work fine provided that they are stable at low impedance.

Transformer coupled amplifiers, tube or solid state, seem to do best with the MartinLogans. I notice that the majority of Best Buy stores demo their MartinLogan speakers using autoformer-coupled McIntosh amplifiers. Pro amplifiers that are designed to be stable into two-ohm loads also can also drive the speakers loudly without any problems. But I wouldn’t want to hook these speakers to an inexpensive AV receiver or to most bridged amplifiers due to the speakers’ impedance and reactance challenges.

The MartinLogan ESL 11A is a world-class speaker. It is revealing, accurate and has the huge soundstage one expects of a dipole radiator. The speaker can sound good with modest source components, but to hear it at its best, use the highest-quality sources and amplifiers that you can provide.

The ESL 11A speakers give a revealing insight into the recording that you’re listening to. Were the microphones overloaded during the recording process? Some Dean Martin recordings were. You’ll hear it through the MLs. Did the recording engineer try to get tricky at the mixing console? You’ll know it. Is the recording compressed for radio play? Is the bass boosted for effect? Is the treble bright? Every one of these recording aspects can be readily heard with the MLs. So if you’re a listener who prefers that your stereo system make everything sound good, be aware that the MLs are not going to editorialize for you – what the speakers get is what you’ll hear – no tricks – no sweetening – nothing hidden.

These Are Excellent Speakers That Come At A High Price. But If You Want Something In The Outer Limits Of What’s Possible In Speaker Technology, Then These Are Relatively Inexpensive Within Their Peer Group.

The MartinLogan ESL 11As are excellent speakers – no question about it. Nor do I know of anything for significantly less money that sounds as transparent. But these days, you can get a really good pair of speakers for $2K. So are these five times as good? No they aren’t. But that doesn’t make them a bad value. IF you have $10K to spend and IF you want something in the outer limits of what’s possible in speaker technology, then these are relatively inexpensive in their peer group of cost-no-object speakers. After all, some speakers are priced at more than $100K per pair! I have heard but few of those, but under no circumstances could a $100K speaker be called a bargain by anyone.

But I have heard other speakers in this $10K price range (in retail venues) – and though some have sounded as good as these in the bass and midrange, none had the ESL 11A’s clean electrostatic sound and huge image. They have true low bass without needing subwoofers. That alone creates a savings of up to 20% of the speakers’ price since good subwoofers are not cheap AND subs normally require a proper electronic crossover and lots of work to integrate.

Further, since the bass amps are built-in on these speakers, you don’t have to buy a super-amplifier of ultra-high wattage to drive them. Low-power amplifiers that sound really good can be had for more modest prices. Being able to use a more modest amplifier saves an additional basket of cash (maybe even another 20%?).

So after the savings on subs & amps, the speakers may be more of a $6K speaker than not. And at that effective price, the ESL 11As become FAR more competitive.

The speakers can be hooked up to an optional electronic room correction system that cleans up the sound of your room. The top panels can be tilted forward or back to provide the best imaging. The speakers look nice (a big issue to some). And they sound great (taken for granted at this price level).

So I’ve evaded the question. Are they worth $10,000? All I can say is that if I could afford them, I might consider buying a pair. They are that good. I’ll be very sorry to see these speakers go!